text: # Stack
  
  # You're now a baseball game point recorder.
  #
  # Given a list of strings, each string can be one of the 4 following types:
  #
  # Integer (one round's score): Directly represents the number of points you get in this round.
  # "+" (one round's score): Represents that the points you get in this round are the sum of the last two valid round's points.
  # "D" (one round's score): Represents that the points you get in this round are the doubled data of the last valid round's points.
  # "C" (an operation, which isn't a round's score): Represents the last valid round's points you get were invalid and should be removed.
  # Each round's operation is permanent and could have an impact on the round before and the round after.
  #
  # You need to return the sum of the points you could get in all the rounds.
  #
  # Example 1:
  # Input: ["5","2","C","D","+"]
  # Output: 30
  # Explanation:
  # Round 1: You could get 5 points. The sum is: 5.
  # Round 2: You could get 2 points. The sum is: 7.
  # Operation 1: The round 2's data was invalid. The sum is: 5.
  # Round 3: You could get 10 points (the round 2's data has been removed). The sum is: 15.
  # Round 4: You could get 5 + 10 = 15 points. The sum is: 30.
  # Example 2:
  # Input: ["5","-2","4","C","D","9","+","+"]
  # Output: 27
  # Explanation:
  # Round 1: You could get 5 points. The sum is: 5.
  # Round 2: You could get -2 points. The sum is: 3.
  # Round 3: You could get 4 points. The sum is: 7.
  # Operation 1: The round 3's data is invalid. The sum is: 3.
  # Round 4: You could get -4 points (the round 3's data has been removed). The sum is: -1.
  # Round 5: You could get 9 points. The sum is: 8.
  # Round 6: You could get -4 + 9 = 5 points. The sum is 13.
  # Round 7: You could get 9 + 5 = 14 points. The sum is 27.
  # Note:
  # The size of the input list will be between 1 and 1000.
  # Every integer represented in the list will be between -30000 and 30000.
  class Solution:
      def calPoints(self, ops):
          """
          :type ops: List[str]
          :rtype: int
          """
          sumList = []
          for i in range(len(ops)):
              if ops[i].lstrip("-").isdigit():
                  sumList.append(int(ops[i]))
              elif ops[i] == '+':
                  firstLast, secondLast = sumList[-1], sumList[-2]
                  sumList.append(firstLast+secondLast)
              elif ops[i] == "D":
                  firstLast = sumList[-1]
                  sumList.append(firstLast * 2)
              elif ops[i] == "C":
                  sumList.pop()
          return sum(sumList)
  